SIP Phones and PBX – Disconnected!

by Dave Michels


Disruptive technologies tend to follow a simple, predictable pattern. First the technology is a niche play – strong benefits, but baggage make it appropriate for specific niches. The digital camera is a good example, they were initially used by journalists that needed to send their photos over phone lines. As the technology gets better/more complete the audience becomes bigger. The key milestone to pass is “as good as the current method”.Once digital camera quality and ease became as good as film cameras, then the market took off. The disruptive nature of technology revolutionized a mature industry. As with all disrruptive technologies, the digital camera changed the basic value proposition – changed the channel (the players, the distributors) and the market dynamics.

I think VoIP, and particularly Astrisk, are disruptive technologies. But business infrastructure change and innovation goes much slower than consumer changes. I was reminded of this on Sunday morning when I found my Polycom phones still on Daylight time.

The phones actually are smart enough to understandDST. I fully expected the time to be right on Sunday morning. In their configuration files theDSToption was enabled, but anotherDSTsetting prevented it from working. I erroneously made the assumption the Switchvox was the problem. The Switchvox was indeed on the correct time. The phones don’t get their time from the PBX as in proprietary phone systems.

I don’t likeDST. I think the whole concept should be a reduced to a historical footnote. I would consider moving toArizonajust to get away from it. I remember the days when Windows computers didn’t change automatically – and UNIX did. We always joked how stupid and primitive Windows PCs were because they could not handle this simple function. I think that got corrected in Windows95 (13 years ago?). The Mitel PBXs still don’t have auto time change – but you can schedule it advance manually. However, as primitive as the Mitel is, at least that single change updates all the clocks on the phones.

The SIP phones don’t get their clock source from the PBX. They connect to a time server on the network, which could be the same server the PBX gets its time from.So, all I have to do is change the SIP phone configuration on the TFTP server and reboot the phones. Not so easy.

First problem is there is no way to centrally reboot the phones from the PBX (that I know of). So I instead rebooted thePOEswitch to reboot all phones. (good thing I was local, most VoIP admins have no problem making changes remotely). I also used the opportunity to update the SIP load on the phones to a later release (seemed low risk). But there was an issue with the new load, so the phones went into continuous reboot (download/save/check/error, reboot). Not sure what that problem was so restored the older load and now things are back up with the right time. Wow. A lot of work to get the clocks right.

I believe that the inability to closely manage and control the phones from the PBX is a major limitation for Asterisk based solutions. The only way to address this in the near term is proprietary SIP extensions or signaling between phones and the PBX. But after going thru ordeals like changing the time, I have to wonder about this whole SIP thing. SIP between the phone and PBX offers little benefit other than the ability to select multiple manufacturers for my phones. I would rather have a more tightly integrated solution – albeit ideally from an open standards approach.

One of the key value props of the Switchvox solution is its simplicity. However, that doesn’t apply to setting options on the phones. Phone configuration is still a nasty esoteric art and the most beautify menu driven GUI on an Asterisk phone system doesn’t offer much here.

This is the irony of the disruptive nature of VoIP. In so many ways it has become so much better than traditional phone systems, but the inability to fully address the features of the way things were has kept VoIP between being a truly disruptive technology and a sustaining technology.

As they say about the metric system…. “America is inching toward it”.